Microelectronic refrigeration system and method

ABSTRACT

A microelectronic refrigeration system is provided for cooling an electronic device. The microelectronic refrigeration system is configured to contain a refrigerant, a low concentration solution, and an intermediary gas. The microelectronic refrigeration system includes: (i) an evaporator configured to be thermally coupled to the electronic device, to receive and vaporize the refrigerant, and to receive the intermediary gas; and (ii) an absorber fluidly coupled to the evaporator. The absorber is configured to receive the low concentration solution and the vaporized refrigerant, which dissolves in the low concentration solution to produce a high concentration solution. The system further includes an intermediary gas return duct fluidly coupled to the evaporator and to the absorber. The intermediary gas return duct is configured to direct the intermediary gas received from the absorber to the evaporator.

TECHNICAL FIELD

The present invention relates generally to microelectronic cooling systems and, more particularly, to a microelectronic refrigeration system and method that employs thermo-chemical compression to cool at least one microelectronic device, such as an integrated circuit.

BACKGROUND

Certain microelectronic devices, such as integrated circuits, are known to generate heat during operation. Such microelectronic devices are commonly cooled to ensure proper functioning and to enable higher operating speeds. A basic microelectronic cooling system may promote convective cooling of a microelectronic device utilizing a fan that directs forced airflow over the device's outer surface. In addition, a heat sink (e.g., a metal body having a substantially flat contact surface and a plurality of projections or fins extending away therefrom) may be placed in thermal contact with the device (e.g., the flat contact surface may be soldered to a substrate supporting the device). During device operation, heat is conducted away from the device and into the projections, which are convectively cooled by exposure to a cooling fluid (e.g., ambient air).

Although fairly reliable and inexpensive to implement, basic cooling systems of the type described above do not achieve optimal device cooling. For this reason, mechanical-compression refrigeration systems have been developed that are significantly more efficient for cooling microelectronic devices. One known mechanical-compression refrigeration system continually supplies a refrigerant, in a liquid state, to the inlet of an evaporator placed in thermal contact with the microelectronic device. Heat generated by the device is conducted to the evaporator and utilized to vaporize the liquid refrigerant. The vaporized refrigerant is then conducted to a mechanical compressor that utilizes a piston or other mechanical means to compress the vaporized refrigerant and thereby return the refrigerant to its liquid state. As the vaporized refrigerant changes phase to liquid, heat is released. This heat is dissipated by convectively cooling the compressor utilizing an external cooling fluid (e.g., ambient air). The liquid refrigerant is then directed back to the inlet of the evaporator, and the process is repeated.

Although relatively efficient at cooling microelectronic devices, mechanical-compression refrigeration systems of the type described above are limited in several respects. For example, the compressor and other components associated with the compressor (e.g., recirculating pumps, throttle valves, etc.) tend to be expensive and unreliable. Furthermore, the use of compressors, throttle valves, recirculating pumps, and the like adds considerable bulk to the refrigeration system that may prevent the refrigeration system from being easily integrated into or packaged with the cooled device. For example, if a conventional mechanical-compression refrigeration system is utilized to cool a computer's central processing unit, it may be difficult to dispose the refrigeration system within the computer's housing.

Accordingly, it is desirable to provide a microelectronic refrigeration system and method that employs a non-mechanical compression means to cool a microelectronic device (e.g., an integrated circuit) and thereby eliminates the need for mechanical compressors, recirculating pumps, throttle valves, and the like. Ideally, such a microelectronic refrigeration system would be relatively compact, thermally efficient, reliable, and inexpensive to produce. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and:

FIG. 1 is a schematic of a microelectronic refrigeration system that utilizes thermo-chemical compression to cool an microelectronic device in accordance with a first exemplary embodiment;

FIGS. 2, 3, 4, and 5 are isometric cross-sectional views of the evaporator, the absorber, the desorber, and the condenser, respectively, employed by the exemplary microelectronic refrigeration system shown in FIG. 1;

FIG. 6 is a schematic of a microelectronic refrigeration system that utilizes thermo-chemical compression to cool a group of microelectronic devices in accordance with a second exemplary embodiment; and

FIGS. 7 and 8 are simplified cross-sectional views of the gas heat exchanger and the liquid heat exchanger, respectively, employed by the exemplary microelectronic refrigeration system shown in FIG. 6.

DETAILED DESCRIPTION

The following Detailed Description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding Background or the following Detailed Description.

FIG. 1 is a schematic of a microelectronic refrigeration system 20 in accordance with an exemplary embodiment. Refrigeration system 20 is suitable for cooling a microelectronic device 22 utilizing a thermo-chemical compression technique. Microelectronic device 22 may comprise any small-scale device that produces heat during operation, such as an integrated circuit or chip. Furthermore, although only one microelectronic device 22 is shown in FIG. 1, it should be readily apparent that microelectronic refrigeration system 20 may be utilized to cool a number of microelectronic devices. Indeed, due to its cooling efficiency, refrigeration system 20 is well-suited for cooling multiple microelectronic devices; embodiments of refrigeration system 20 are capable of maintaining high-power systems (e.g., with powers up to approximately 200 watts and, preferably, ranging from about 20 watts to about 100 watts) at relatively low temperatures (e.g., 25 degrees Celsius) during operation.

In the exemplary embodiment shown in FIG. 1, refrigeration system 20 comprises four principal components: (1) an evaporator 24, (2) an absorber 26, (3) a desorber 28, and (4) a condenser 30. Evaporator 24, absorber 26, desorber 28, and condenser 30 are fluidly coupled in series by way of a plurality of flow passages. In particular, a first flow passage 32 fluidly couples an outlet of evaporator 24 to an inlet of absorber 26; a second flow passage 34 fluidly couples an outlet of absorber 26 to an inlet of desorber 28; a third flow passage 36 fluidly couples an outlet of desorber 28 to an inlet of condenser 30; and, to complete the flow circuit, a fourth flow passage 38 fluidly couples an outlet of condenser 30 to an inlet of evaporator 24. In addition to flow passages 32, 34, 36, and 38, refrigeration system 20 includes first and second return ducts 40 and 42. In the instant embodiment, return duct 40 is coupled between an outlet of absorber 26 and flow passage 38 (upstream of evaporator 24), and return duct 42 is coupled between an outlet of desorber 28 and an inlet of absorber 26. As described in detail below, return duct 40 conducts an intermediary gas during operation of refrigeration system 20 and may consequently be referred to as “intermediary gas return duct 40.” Furthermore, return duct 42 conducts a low concentration solution and may thus be referred to as “low concentration solution return duct 42.” Finally, return ducts 40 and 42, evaporator 24, absorber 26, desorber 28, condenser 30, and flow passages 32, 34, 36, and 38 may be collectively referred to as “the flow assembly.”

As indicated in FIG. 1 at 44, evaporator 24 is placed in thermal contact with microelectronic device 22 such that heat generated by device 22 is conducted, at least in part, to evaporator 24. If, for example, microelectronic device 22 comprises an integrated circuit, evaporator 24 may be placed in direct contact with the circuit or with another component in thermal communication therewith (e.g., a copper bonding pad provided on the circuit's substrate). Alternatively, if microelectronic device 22 is contained within an encapsulated package, evaporator 24 may be placed in contact with an outer surface of the encapsulant.

FIG. 2 is a cross-sectional isometric view of evaporator 24 in accordance with an exemplary embodiment. In this view, it can be seen that evaporator 24 comprises a flowbody 44 formed from a thermally-conductive material (e.g., copper, nickel, etc.) and having first and second opposing outer surfaces 46 and 48. When refrigeration system 20 is installed, outer surface 48 contacts microelectronic device 22 (or another structure in thermal communication therewith) such that heat is conducted away from device 22 and into flowbody 44 of evaporator 24. To optimize thermal conduction, outer surface 48 is preferably characterized by a smooth and flat geometry. In addition, the shape of flowbody 44 may be generally rectangular to maximize the surface area of outer surface 48 relative to the overall dimensions of flowbody 44.

A plurality of channels 50 extends through flowbody 44 of evaporator 24. During operation of refrigeration system 20, channels 50 conduct a refrigerant supplied to an inlet of evaporator 24 in a liquid state. As evaporator 24 conductively absorbs heat from microelectronic device 22, flowbody 44 reaches a temperature sufficient to vaporize the refrigerant flowing through channels 50. The refrigerant absorbs heat as it vaporizes thus dissipating heat from flowbody 44 and, therefore, microelectronic device 22. To cause the vaporized refrigerant to flow downward from evaporator 24, through flow passage 32, and into absorber 26, an intermediary gas is introduced into an inlet of evaporator 24. In a preferred embodiment, the intermediary gas bonds with the refrigerant to yield a gas-refrigerant composition. The molecules of the gas-refrigerant composition are heavier than those of the refrigerant. As absorber 26 is located at a position that is lower than the position of evaporator 24, the gas-refrigerant composition flows downward under the influence of gravity through an outlet of evaporator 24, through flow passage 32, and into an inlet of absorber 26.

Although a preferred embodiment has been described wherein the intermediary gas bonds with the refrigerant to yield a gas-refrigerant composition, the intermediary gas may not bond with the refrigerant in alternative embodiments. Instead, the intermediary gas may simply mix with the refrigerant to create a pressure differential that draws the vaporized refrigerant downward through flow passage 32 and into absorber 26. Thus, regardless of whether bonding does or does not occur between the intermediary gas and the refrigerant, the refrigerant flows downward into absorber 26 wherein the refrigerant is dissolved into a solvent in the manner described below.

Within absorber 26, the refrigerant is exposed to a low concentration binary solution, which is supplied to an inlet of absorber 26 by low concentration solution return duct 42. The low concentration binary solution comprises a solvent having a relatively small amount of the refrigerant dissolved therein. The boiling point of the solvent is greater than that of the refrigerant. The refrigerant dissolves, at least partially, in the solvent to produce a high concentration binary solution. If the refrigerant has bonded with the intermediary gas to produce a gas-refrigerant composition, the gas dissociates from the refrigerant as the refrigerant dissolves into the solvent. As the refrigerant dissolves into the solvent, the refrigerant's phase changes to liquid and heat is generated. The generated heat is dissipated by convection to an external cooling fluid, which may be, for example, ambient air. Convective cooling may be promoted by a micro-fan 52, which, when energized, directs forced airflow over absorber 26. As a result of this chemical dissolution process, the vaporized refrigerant's phase is returned to a liquid state without the use of a mechanical compressor and other components (e.g., pumps, throttle valves, etc.) commonly associated therewith.

FIG. 3 is a cross-sectional isometric view of an absorber 26 in accordance with an exemplary embodiment. Absorber 26 includes a flowbody 54 (e.g., copper) through which a plurality of channels 56 extends. During operation of refrigeration system 20, channels 56 conduct the gas, the refrigerant, and the low concentration solution. If the gas and refrigerant have bonded to produce a gas-refrigerant composition, the gas-refrigerant composition and the low concentration solution interact in the manner described above to yield dissociated intermediary gas and high concentration solution. As noted above, heat generated during the dissolution process is convectively transferred from flowbody 54 to an external cooling fluid, such as ambient air. To maximize surface area of flowbody 54, and thereby enhance the convective cooling of absorber 26, first and second pluralities of projections 58 and 60 (commonly referred to as “pin-fins”) are fixedly attached to opposing faces of flowbody 54. More specifically, and with reference to the orientation shown in FIG. 3, projections 58 and 60 are fixedly attached to the upper and lower faces, respectively, of flowbody 54. As indicated above, a fan (e.g., micro-fan 52 shown in FIG. 1) may be employed to provide forced airflow over projections 58 and/or projections 60.

Intermediary gas return duct 40 (FIG. 1) collects the intermediary gas from absorber 26 and redirects the intermediary gas back to flow passage 38. The intermediary gas subsequently flows into evaporator 24, and the above-described process is repeated. The continuous upward-downward circulation of the intermediary gas helps to maintain a substantially constant pressure throughout refrigeration system 20 that is substantially equivalent to the condensing pressure of the vaporized refrigerant.

From absorber 26, the high concentration solution flows through flow passage 34 and into desorber 28. As shown in FIG. 1, an external heat source 62 is thermally coupled to desorber 28. As desorber 28 receives the high concentration binary solution from flow passage 34, heat source 62 heats desorber 28, and therefore the high concentration solution, to a temperature above the refrigerant's boiling point and below the solvent's boiling point. The refrigerant consequently vaporizes to a gaseous state and dissociates, in large part, from the solvent to yield vaporized refrigerant and a low concentration binary solution. The vaporized (gaseous) refrigerant flows from desorber 28, through flow passage 36, and into condenser 30 wherein the refrigerant is again condensed to a liquid state in the manner described below. The low concentration solution flows into low concentration solution return duct 42, which directs the low concentration back to an inlet of absorber 26 thus permitting the above-described dissolution process to repeat.

FIG. 4 is a cross-sectional isometric view of desorber 28. In this exemplary embodiment, desorber 28 is structurally similar to evaporator 24 described above in conjunction with FIG. 2, although it should be appreciated that the orientation of desorber 28 preferably varies from that of evaporator 24 to accommodate the upward flow of the vaporized refrigerant from flow passage 34 to flow passage 36. For example, desorber 28 comprises a flowbody 64 having a plurality of channels 66 formed therethrough. During operation of refrigeration system 20, channels 66 conduct the high concentration binary solution through flowbody 64. A heat source (e.g., heat source 62 shown in FIG. 1) heats flowbody 64, and thus the high concentration solution, to a temperature above the refrigerant's boiling point to evaporate the refrigerant from the solvent in the manner described above. The heat source 62 may comprise any device suitable for heating flowbody 64 to such a temperature. For example, and as indicated in FIG. 1, heat source 62 may comprise an electrical resistor (a heater). Alternatively, heat source 62 may comprise a heat-generating component of another microelectronic device disposed proximate refrigeration system 20.

FIG. 5 is an isometric cross-sectional view of a condenser 30 suitable for utilization in exemplary refrigeration system 20 (FIG. 1). As may be appreciated by comparing FIG. 5 to FIG. 3, condenser 30 is structurally similar to absorber 26; e.g., condenser 30 includes a flowbody 68 having a plurality of flow channels 70 therethrough. During operation flowbody 68 receives the refrigerant, in a gaseous state, from flow passage 36. The refrigerant condenses within channels 70 to a liquid state resulting in the release of heat. The released heat is imparted to flowbody 68, which is, in turn, convectively cooled by an external cooling fluid, such as air. As was the case previously, first and second pluralities of projections 72 and 74 (“pin-fins”) may be attached to opposing faces of flowbody 68 to increase the convective cooling of condenser 30. Additionally, and as shown in FIG. 1, a micro-fan 76 may be positioned near condenser 30 to provide forced airflow over projections 72 and/or projections 74. In the exemplary case wherein device 22 assumes the form of an integrated circuit supported by a printed circuit board (PCB), condenser 30 is preferably mounted to the underside of the PCB substantially opposite evaporator 82. The condensed refrigerant then flows from condenser 30, through flow passage 38, and into evaporator 24, and the above-described thermo-chemical compression process repeats to continually dissipate excess heat generated by microelectronic device 22.

It should thus be appreciated that there has been provided an exemplary embodiment of a refrigeration system 20 suitable for cooling one or more microelectronic devices (e.g., device 22 shown in FIG. 1). Refrigeration system 20 is thermally efficient, reliable, and relatively inexpensive to produce. In addition, refrigeration system 20 utilizes a thermo-siphoning process to continually circulate the chosen refrigerant and, thus, does not require the use of mechanical compressors and recirculating pumps, which tend to be bulky, expensive, and unreliable. Furthermore, the pressure throughout refrigeration system 20 maintains an average internal pressure substantially equivalent to the condensation pressure thereby eliminating the need for bulky throttle valves. This notwithstanding, embodiments of refrigeration system 20 may be implemented with pumps and/or throttle valves to provide more efficient cooling for microelectronic devices operating at significant power thresholds (e.g., exceeding 200 watts). Although the precise dimensions will inevitably vary amongst different embodiments, the components of refrigeration system 20 may generally be manufactured to relatively small dimensions. Evaporator 24, in particular, may be miniaturized to a scale similar to that of the integrated chip (or other microelectronic device) to be cooled.

One skilled in the art will readily appreciate a variety of substances may be chosen to serve as the refrigerant, the intermediary gas, and the solvent. Obviously, the particular refrigerant, intermediary gas, and solvent chosen will vary in relation to one another and in relation to the overall chemistry of the refrigeration system. For example, the boiling point of the chosen refrigerant should be less than that of the chosen solvent, and the chosen intermediary gas preferably does not readily chemically interact with the chosen solvent. A non-exhaustive list of suitable refrigerants includes ammonia and hydrochlorofluorocarbon (e.g., Freon®). A non-exhaustive list of suitable intermediary gasses includes hydrogen, argon, and helium. In one preferred embodiment of the refrigeration system, the chosen refrigerant comprises ammonia (NH₃), the chosen intermediary gas comprises hydrogen (H₂), and the chosen solvent comprises water (H₂O). In this exemplary case, the hydrogen will bond with the ammonia within the evaporator to yield ammonium cations (NH₄ ⁻) as a gas-refrigerant composition, although, as previously explained, the refrigerant may not bond with the intermediary gas in certain embodiments of the cooling system.

Microelectronic refrigeration system 20 is but one example of a particular form that may be assumed by the inventive refrigeration system; numerous structural changes, including the addition and removal of components, may be made to refrigeration system 20 without departing from the scope of the invention as set-forth in the appended claims. To further emphasize this point, FIG. 6 schematically illustrates a second exemplary microelectronic refrigeration system 78 utilized to cool a plurality of microelectronic devices 80, which may or may not populate the same printed circuit board. In many aspects, microelectronic refrigeration system 78 is similar to microelectronic refrigeration system 20. As does refrigeration system 20, microelectronic refrigeration system 78 includes a first evaporator 82 (in thermal contact with one of microelectronic devices 80), an absorber 84, a desorber 86, and a condenser 88 that are fluidly coupled in series via a plurality of flow passages 90, 92, 94, 96. Microelectronic cooling system 78 further includes an intermediary gas return duct 100 and a low concentration solution return duct 102. Intermediary gas return duct 100 is fluidly coupled between absorber 84 and flow passage 96 (upstream of evaporator 82); and low concentration solution return duct 102 is fluidly coupled between desorber 86 and absorber 84. As was the case previously, first and second micro-fans 104 and 106 are provided to promote the convective cooling of absorber 84 and condenser 88, respectively. The function and general structural design of the evaporator, absorber, desorber, and condenser have been described above in detail. The manner in which the evaporator, absorber, desorber, and condenser cooperate to form a thermo-siphon that continually circulates a phase-change refrigerant to cool microelectronic devices 80 has also been described above and will thus not be discussed at this junction.

Microelectronic refrigeration system 78 differs from refrigeration system 20 (FIG. 1) in two general manners. First, refrigeration system 78 is equipped with a second evaporator 108 in addition to first evaporator 82. Evaporator 108 is fluidly coupled to flow passages 90 and 96 via flow passages 98 and thermally coupled to multiple microelectronic devices 80. Microelectronic refrigeration system 78 is illustrated as including second evaporator 108 to further emphasize that embodiments of the refrigeration system are well-suited for cooling multiple devices utilizing one evaporator or multiple evaporators. Microelectronic refrigeration system 78 also differs from refrigeration system 20 in a second manner, as well; i.e., microelectronic refrigeration system 78 includes first and second heat exchangers 110 and 112. As described in detail below, heat exchanger 110 facilitates the exchange of heat between the gas-refrigerant composition flowing through flow passage 90 and the intermediary gas flowing through return duct 100. As both of these substances are in a gaseous state, heat exchanger 110 may be referred to as “gas heat exchanger 110.” By comparison, heat exchanger 112 facilitates the exchange of heat between the high concentration solution flowing through flow passage 92 and the low concentration solution flowing through return duct 102. For this reason, heat exchanger 112 may be referred as “liquid heat exchanger 112.”

FIG. 7 is a simplified cross-sectional view of gas heat exchanger 110 in accordance with an exemplary embodiment. As can be seen, gas heat exchanger 110 comprises a flowbody 114 defining an internal cavity 116. Flow passage 90, which conducts the gas-refrigerant composition, passes through flowbody 114 and is generally surrounded by cavity 116. During operation of refrigeration system 78, intermediary gas flowing from absorber 84 to evaporator 82 is directed through cavity 116 by intermediary gas return duct 100. Within gas heat exchanger 110, the gas-refrigerant composition flowing through flow passage 90 cools the intermediary gas flowing through internal cavity 116. At the same time, the intermediary gas pre-heats the gas-refrigerant composition before the gas-refrigerant composition flows into absorber 84. By permitting the cooling of the intermediary gas and the pre-heating of the gas-refrigerant composition, gas heat exchanger 110 increases the overall thermal efficiency of refrigeration system 78.

FIG. 8 is a simplified cross-sectional view of liquid heat exchanger 112 in accordance with an exemplary embodiment. In this example, liquid heat exchanger 112 is substantially identical to gas heat exchanger 110; e.g., liquid heat exchanger 112 comprises a flowbody 118 defining an internal cavity 120. Flow passage 92, which conducts the high concentration solution, passes through flowbody 118 and is generally surrounded by cavity 120. During operation, return duct 102 supplies low concentration solution to, and receives low concentration solution from, cavity 120. The low concentration solution pre-heats the high concentration solution flowing through flow passage 92 and thereby promotes the vaporization of the refrigerant within desorber 86. This again increases the overall thermal efficiency of refrigeration system 78.

In view of the above, it should be appreciated that multiple exemplary embodiments have been provided of a microelectronic refrigeration system and method suitable for thermo-chemically cooling a microelectronic device without the use of a mechanical compressor or other components (e.g., recirculating pumps, throttle valves, etc.) commonly associated therewith. Advantageously, embodiments of the microelectronic refrigeration system are relatively compact, thermally efficient, reliable, and inexpensive to produce. Although a preferred embodiment has been described above wherein the refrigerant bonds with the intermediary gas to produce a gas-refrigerant composition, alternative embodiments may employ a refrigerant that does not bond with the intermediary gas.

In a first embodiment, a microelectronic refrigeration system is provided for cooling an electronic device. The microelectronic refrigeration system is configured to contain a refrigerant, a low concentration solution, and an intermediary gas. The microelectronic refrigeration system includes: (i) an evaporator configured to be thermally coupled to the electronic device, to receive and vaporize the refrigerant, and to receive the intermediary gas; and (ii) an absorber fluidly coupled to the evaporator. The absorber is configured to receive the low concentration solution and the vaporized refrigerant, which dissolves in the low concentration solution to produce a high concentration solution. The system further includes an intermediary gas return duct fluidly coupled to the evaporator and to the absorber. The intermediary gas return duct is configured to direct the intermediary gas received from the absorber to the evaporator.

In addition to the above-described components, the microelectronic refrigeration system may further include: (i) a desorber fluidly coupled to the absorber and configured to receive the high concentration solution therefrom, (ii) a heat source thermally coupled to the desorber and configured to heat the desorber to evaporate a portion of the refrigerant from the high concentration solution to yield a low concentration solution, and (iii) a low concentration solution return duct fluidly coupled between the desorber and the absorber, the low concentration solution return duct directing the low concentration solution received from the desorber back to an inlet of the absorber. A condenser may be fluidly coupled between the desorber and configured to condense the vaporized refrigerant to a liquid state. A flow passage may also be fluidly coupled between the absorber and the desorber, and a solution heat exchanger may be fluidly coupled to the flow passage and to the low concentration solution return duct. Furthermore, a flow passage fluidly may be coupled between the evaporator and the absorber, and a gas heat exchanger fluidly may be coupled to the flow passage and to the intermediary gas return duct. Lastly, in an embodiment wherein the electronic device comprises an integrated circuit supported by a printed circuit board, the evaporator and the condenser may be mounted to opposing surfaces of the printed circuit board.

In accordance with a second exemplary embodiment, a microelectronic refrigeration system is provided for cooling an electronic device. The microelectronic refrigeration system is configured to contain an intermediary gas. The microelectronic refrigeration system includes a flow assembly that contains a solvent and a refrigerant, which is dissolvable in the solvent. The flow assembly includes: (i) an evaporator configured to be thermally coupled to the electronic device, (ii) an absorber fluidly coupled to the evaporator, and (iii) a first return duct fluidly coupled to the absorber and to the evaporator. The absorber is located at a position in the flow assembly that is lower than the position of the evaporator. The flow assembly is configured such that the intermediary gas causes the downward flow of the refrigerant from the evaporator to the absorber.

In a further embodiment, the boiling point of the refrigerant is less than that of the solvent. In another embodiment, the refrigeration system further includes: (i) a desorber fluidly coupled to the absorber, (ii) a heat source thermally coupled to the desorber, and (iii) a condenser fluidly coupled between the desorber and the evaporator. The system may also include a second return duct fluidly coupled to the desorber and to the absorber. In one implementation, the flow assembly is structurally arranged such that the solvent circulates from the absorber, through the desorber, and through the second return duct before returning to the absorber. In further implementation, the flow assembly is structurally arranged such the intermediary gas circulates from the evaporator, through the absorber, and through the first return duct before returning to the absorber. In a still further implementation, the flow assembly is structurally arranged such that the refrigerant circulates from the evaporator, through the absorber, through the desorber, and through the condenser before returning to the evaporator. The heat source may comprise an electrical resistor. The system may further include a flow passage fluidly coupled between the evaporator and the absorber, and a gas heat exchanger fluidly coupled to the flow passage and to the first return duct. In accordance with a further embodiment, a flow passage is fluidly coupled between the absorber and the desorber, and a liquid heat exchanger is fluidly coupled to the flow passage and to the second return duct. The solvent may comprise water, and the refrigerant may comprise ammonia.

In accordance with a still further embodiment, a method is provided for cooling a microelectronic device that generates heat during operation. The method includes the steps of vaporizing a refrigerant utilizing the generated heat, introducing an intermediary gas that reacts with the refrigerant to produce a gas-refrigerant composition, and exposing the gas-refrigerant composition to a solvent such that the gas dissociates from the gas-refrigerant composition and the refrigerant dissolves in the solvent to produce a high concentration solution. This results in a refrigerant phase change from gas to liquid. The high concentration solution is heated to evaporate the refrigerant from the gas-refrigerant solution to yield a low concentration solution and a vaporized refrigerant, and the vaporized refrigerant is condensed to return the refrigerant to a liquid state. In certain embodiments, the method may further include the step of selecting the intermediary gas from the group consisting of hydrogen, argon, and helium.

While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents. 

1. A microelectronic refrigeration system for cooling an electronic device, the microelectronic refrigeration system configured to contain a refrigerant, a low concentration solution, and an intermediary gas, the microelectronic refrigeration system comprising: an evaporator configured to be thermally coupled to the electronic device, to receive and vaporize the refrigerant, and to receive the intermediary gas; an absorber fluidly coupled to the evaporator, the absorber configured to receive the vaporized refrigerant and the low concentration solution, the vaporized refrigerant dissolving in the low concentration solution to produce a high concentration solution; and an intermediary gas return duct fluidly coupled to the evaporator and to the absorber, the intermediary gas return duct configured to direct the intermediary gas received from the absorber to the evaporator.
 2. A microelectronic refrigeration system according to claim 1 further comprising: a desorber fluidly coupled to the absorber and configured to receive the high concentration solution therefrom; a heat source thermally coupled to the desorber and configured to heat the desorber to evaporate the refrigerant from the high concentration solution to yield a low concentration solution; and a low concentration solution return duct fluidly coupled between the desorber and the absorber, the low concentration solution return duct directing the low concentration solution received from the desorber back to an inlet of the absorber.
 3. A microelectronic refrigeration system according to claim 2 further comprising a condenser fluidly coupled between the desorber and the evaporator, the condenser configured to condense the vaporized refrigerant to a liquid state.
 4. A microelectronic refrigeration system according to claim 2 further comprising: a flow passage fluidly coupled between the absorber and the desorber; and a solution heat exchanger fluidly coupled to the flow passage and to the low concentration solution return duct.
 5. A microelectronic refrigeration system according to claim 2 further comprising: a flow passage fluidly coupled between the evaporator and the absorber; and a gas heat exchanger fluidly coupled to the flow passage and to the intermediary gas return duct.
 6. A microelectronic refrigeration system according to claim 3 wherein the electronic device comprises an integrated circuit supported by a printed circuit board, and wherein the evaporator and condenser are mounted to opposing surfaces of the printed circuit board.
 7. A microelectronic refrigeration system for cooling an electronic device, the microelectronic refrigeration system configured to contain an intermediary gas, the microelectronic refrigeration system comprising: a flow assembly, comprising: an evaporator configured to be thermally coupled to the electronic device; an absorber fluidly coupled to the evaporator, the absorber located at a position in the flow assembly that is lower than the position of the evaporator; and a first return duct fluidly coupled to the absorber and to the evaporator; a solvent disposed in the flow assembly; and a refrigerant disposed in the flow assembly and dissolvable in the solvent; wherein the flow assembly is configured such that the intermediary gas causes the downward flow of the refrigerant from the evaporator to the absorber.
 8. A microelectronic refrigeration system according to claim 7 wherein the boiling point of the refrigerant is less than that of the solvent.
 9. A microelectronic refrigeration system according to claim 7 further comprising: a desorber fluidly coupled to the absorber; a heat source thermally coupled to the desorber; and a condenser fluidly coupled between the desorber and the evaporator.
 10. A microelectronic refrigeration system according to claim 9 further comprising a second return duct fluidly coupled to the desorber and to the absorber.
 11. A microelectronic refrigeration system according to claim 10 wherein the flow assembly is structurally arranged such that the solvent circulates from the absorber, through the desorber, and through the second return duct before returning to the absorber.
 12. A microelectronic refrigeration system according to claim 7 wherein the flow assembly is structurally arranged such the intermediary gas circulates from the evaporator, through the absorber, and through the first return duct before returning to the absorber.
 13. A microelectronic refrigeration system according to claim 9 wherein the flow assembly is structurally arranged such that the refrigerant circulates from the evaporator, through the absorber, through the desorber, and through the condenser before returning to the evaporator.
 14. A microelectronic refrigeration system according to claim 9 wherein the heat source comprises an electrical resistor.
 15. A microelectronic refrigeration system according to claim 7 further comprising: a flow passage fluidly coupled between the evaporator and the absorber; and a gas heat exchanger fluidly coupled to the flow passage and to the first return duct.
 16. A microelectronic refrigeration system according to claim 9 further comprising: a flow passage fluidly coupled between the absorber and the desorber; and a liquid head exchanger fluidly coupled to the flow passage and to the second return duct.
 17. A microelectronic refrigeration system according to claim 7 wherein the solvent comprises water.
 18. A microelectronic refrigeration system according to claim 17 wherein the refrigerant comprises ammonia.
 19. A method for cooling a microelectronic device that generates heat during operation, the method comprising: vaporizing a refrigerant utilizing the generated heat; introducing an intermediary gas that reacts with the refrigerant to produce a gas-refrigerant composition; exposing the gas-refrigerant composition to a solvent such that the gas dissociates from the gas-refrigerant composition and the refrigerant dissolves in the solvent to produce a high concentration solution; heating the high concentration solution to evaporate the refrigerant from the gas-refrigerant solution to yield a low concentration solution and a vaporized refrigerant; and condensing the vaporized refrigerant to return the refrigerant to a liquid state.
 20. A method according to claim 19 further comprising the step of selecting the intermediary gas from the group consisting of hydrogen, argon, and helium. 